Transcript Males compete to be chosen by a female

Mating Tactics and Mating Systems
Basic components of sexual reproduction in animals
•Courtship?
•Fertilization
•Parental Care?
Hermaphroditic earthworms exchange sperm;
both leave their fertilized eggs in cocoons
Female horseshoe crab laying eggs;
ten males are fertilizing them
(Grier 1984)
Male Banded Jawfish
orally brooding its eggs.
Male retrieves female’s
spawn and incubates the
eggs until they hatch.
He leaves eggs in
burrow briefly to feed
himself.
Courtship and sperm transfer in pygmy salamander. Male judges her receptiveness by
presence of her chin on his tail, then deposits spermatophore. Both move forward and
she recovers spermatophore in her vent while he arches his tail.
Parental care in female dusky salamander.. She rotates eggs and prot
them from fungal infections and predation by arthropods and other
salamanders
Female cheetah stands guard as her two cub feed on a kill.
Sexual Selection
•Natural Selection: Differential reproductive success.
•Sexual Selection: Differential reproductive success that
results from advantages in attracting or competing for
mates.
Reproduction; Individuals Engaged in Cooperation and Conflict
•Between partners
•Between parents and
offspring
(Solomon et al 1999)
Mating Tactics and Mating Systems
Basic mating “systems” in animals
Pair bond, relationship forms;
•Monogamous relationship; one male and one female
•Polygamous relationship;
•Polygyny; one male and two or more females
•Polyandry; one female and two or more males
No pair bond, no relationship
•Promiscuity
Female Brown Kiwi
(Gill 1995)
Anisogamy
•Females produce limited number of energy expensive gametes
•Males produce virtually unlimited number of small, inexpensive
gametes
Sexual generalization on mating tactics
•Females, having limited number of gametes to pass on to next
generation, tend to be selective, choosy, to get high quality male,
to maximize reproductive contribution to next generation.
•Males, conversely, may maximize reproductive contribution by
being rather non-selective, inseminating as many females as
possible
Anisogamy, Sexual Selection, explain broad patterns of mating
behavior
•Males typically initiate courtship
•Males typically compete with each other for females
•Males compete to be chosen by a female; often involves highly
ritualized displays, ornate coloring of males
•Males compete for exclusive access to females; often involves
ritualized or real aggression and physical combat, where males use
large body size, antlers, spurs, etc., as weapons
Intense competition to be a successful breeder is sexual selection;
evolutionary consequence is exaggerated traits
•Ritualized displays
•Ornate plumage, pelage, etc.
•Fighting gear and large body size
(Raven and Johnson 1999)n
Male Anolis Lizard. Hormonal stimulation prompts males to extend
fleshy dewlap to court females. This behavior stimulates hormone
release and egg-laying in the female; it’s a sign stimulus/releaser.
Male elephant seals engage in mock battle for females.
Male armament; products of
sexual selection
Moose skull
Male hercules beetle
from South America
Male and female
Lucanid beetles
(Grier 1984)
Male Great Frigatebird inflates
his red throat sac as part of
courtship ritual
Male and female Egret performing
highly ritualized courtship dance.
Solomon et. al. 1999)
Cooperation among Florida Scrub Jays. Helpers at the
nest are young from previous seasons that have stayed on
to help parents with feeding, territory defense, predator
defence, etc., instead of attempting to breed themselves.
Coefficient of relatedness, r, is the probability that an allele in one
individual is identical, by descent, to an allele in another individual.